This invention relates to a method and apparatus for improving the speed and fuel economy of manned and unmanned vehicles and in particular power systems thereof. This invention also relates to a method and apparatus for altering the acoustic signature economy of manned and unmanned vehicles.
A cross section of a sub surface vessel known in the art is shown in FIG. 1. The drive train described within FIG. 1 is also applicable to surface vessels. It is common for surface and subsurface vessels to be powered by a nuclear or diesel driven electric generator or batteries. The propulsion system of the subsurface vessel 1 includes a nuclear or diesel driven electric generator or battery pack 2 which produces either alternating current or direct current electricity except for batteries which only produce direct current. The alternating current or direct current electricity is in turn delivered to the motor 8 by means of wires 6 and 7. The output shaft 9 of the electric motor 8 is supported by means of a bearing 10 and has a propeller 11 affixed to it. When AC or DC electricity is applied to the electric motor 8, the shaft of an electric motor 9 begins to rotate and accelerate to a uniform rotational velocity (rpm) thereby causing the propeller 11 to spin. The rotation of the propeller 11 in turn causes the fluid 12 within which the vessel 1 is suspended to be ejected from the propeller 11 in a direction 13 when the vessel 1 wishes to move forward in the direction 14. By reversing the direction of rotation of the electric motor 8 the fluid 12 within which the vessel is suspended would flow in direction 10 from the propeller 11 thereby causing the vessel 1 to move in the direction 13. In this arrangement, the cavitation of the propeller and the mechanical resonance of the generator, electric motor and associated mechanical linkages produce a distinct and characteristic noise xe2x80x9csignaturexe2x80x9d which can be used to identify the vessel and determine its approximate speed. Furthermore, this system cannot achieve a thermodynamic efficiency in excess of 40%, and typically less than 30%.
A cross section of another design of subsurface vessel known in the art is shown in FIG. 2. The drive train described within FIG. 2 is also applicable to surface vessels. It is common for surface and subsurface vessels to be powered by a nuclear or diesel driven electric generator or batteries. The propulsion system of the subsurface vessel 15 includes a nuclear or diesel driven electric generator 16 which produces either alternating current or direct current electricity except for batteries which only produce direct current. The alternating current or direct current electricity is in turn delivered to the motor 17 by means of wires 18 and 19. The output shaft 20 of the electric motor 17 is coupled to a clutch 21 which selectively engages and disengages the electric motor 17 from the gear box 24. The output shaft 23 the clutch 21 is coupled with the gear box 24 whose output shaft 25 has the propeller 22 affixed thereto. A bearing 26 supports the output shaft from the gear box 24. The purpose of the gear box 24 is to reduce the high rotational speed from the shaft 20 of the motor 17 to a rotational speed suitable for driving the propeller 22. When AC or DC electricity is applied to the electric motor 17, the shaft of a electric motor 20 begins to rotate and accelerate to a uniform rotational velocity (rpm). When the clutch 21 is engaged the rotational energy of the electric motor is transferred to the gear box 24 by means of shaft 23 which in turn causes shaft 25 to spin which thereby causes the propeller 22 to spin. The rotation of the propeller 22 in turn causes the fluid 27 within which the vessel 15 is suspended to be ejected from the propeller 22 in a direction 28 when the vessel 15 wishes to move forward in the direction 29. By reversing the direction of rotation of the electric motor 17 the fluid 27 within which the vessel 15 is suspended would flow in direction 29 from the propeller 22 thereby causing the vessel 15 to move in the direction 28. Alternately, the position of the clutch 21 and the gear head 24 may be reversed in their mechanical connection. In this embodiment, the cavitation of the propeller and the mechanical resonance of the generator, electric motor and associated mechanical linkages produce a distinct and characteristic noise xe2x80x9csignaturexe2x80x9d which can be used to identify the vessel and determine its approximate speed. Furthermore, this system cannot be achieve a thermodynamic efficiency in excess of 40%, and typically less than 30%.
A cross section of a design for a surface vessel known in the art is shown in FIG. 3. The drive train described within FIG. 3 could be applicable to subsurface and other vessels. It is common for surface vessels to be powered by diesel or gasoline engine 30. The propulsion system of the surface vessel 30 includes a diesel or gasoline engine 31. The output shaft 32 of the diesel or gasoline engine 31 is coupled to a clutch 33 which selectively engages and disengages the diesel or gasoline engine 31 from the gear box 33. The output shaft 34 of the clutch 32 is coupled with the gear box 35 whose output shaft 36 has the propeller 37 affixed thereto. A bearing 38 supports the output shaft 36 from the gear box 35. The purpose of the gear box 35 is to reduce the high rotational speed from the shaft 20 of the diesel or gasoline engine 31 to a rotational speed suitable for driving the propeller 37. When the diesel or gasoline engine 31 is started, the output shaft 32 of the diesel or gasoline engine 31 begins to rotate and accelerate to a uniform rotational velocity (rpm). When the clutch 33 is engaged the rotational energy of the diesel or gasoline engine 31 is transferred to the gear box 35 by means of shaft 34 which in turn causes shaft 36 to spin which thereby causes the propeller 37 to spin. The rotation of the propeller 37 in turn causes the fluid 39 within which the vessel 30 is immersed to be ejected from the propeller 37 in a direction 40 when the vessel 30 wishes to move forward in the direction 41. By reversing the direction of rotation of the propeller 37, the fluid 39 within which the vessel 30 is immersed would flow in direction 41 from the propeller 37 thereby causing the vessel 30 to move in the direction 40. In this arrangement, the cavitation of the propeller and the mechanical resonance of the generator, electric motor and associated mechanical linkages produce a distinct and characteristic noise xe2x80x9csignaturexe2x80x9d which can be used to identify the vessel and determine its approximate speed. Alternately, the position of the clutch 33 and the gear head 35 may be reversed in their mechanical connection. Furthermore, this system cannot be achieve a thermodynamic efficiency in excess of 40%, and typically less than 30%.
A cross section of a design for a torpedo known in the art is shown in FIG. 4. It is common for a torpedo to be powered by a combustion engine 42 which receives self-oxidizing fuel from a fuel reservoir 43 by means of a fuel pump 44 which delivers a steady stream of fuel through tube 45. The combustion engine 42 causes a constant rotation of the shaft 46 which is supported by bearing 47 and to which propeller 48 is affixed. The guidance and control systems of such a device are not of concern in this invention and any known in the art may be used. When the combustion engine 42 is started, the output shaft 46 begins to rotate and accelerate to a uniform rotational velocity (rpm). The rotational energy of the combustion engine 42 is transferred to the propeller 48 by means of shaft 46. The rotation of the propeller 48 in turn causes the fluid 49 within which the torpedo 42 is immersed to be ejected from the propeller 48 in a direction 50 which causes the torpedo 42 to move forward in the direction 51. In this embodiment, the cavitation of the propeller and the mechanical resonance of the generator, electric motor and associated mechanical linkages produce a distinct and characteristic noise xe2x80x9csignaturexe2x80x9d which can be used to identify the torpedo and determine its approximate speed. Furthermore, this embodiment cannot be a thermodynamic efficiency in excess of 40%, and typically less than 30%.
This invention relates to a method and apparatus for improving the speed and fuel economy of aircraft, surface vessels, sub-surface vessels, missiles and torpedoes. This invention also provides a method and apparatus for altering the acoustic signature of such aircraft, surface vessels, sub-surface vessels, missiles or torpedoes which is of tactical military utility.
By way of example, and without being limited in the future by theory, as a fluid including air or water passes over a fluid moving member such as a propeller, impeller, turbine, blade or the like, a Prandtl layer forms along the fluid moving member as well as a series of additional boundary layers. For a given fluid moving member velocity, a specific number of boundary layers of a given thickness form. The upper boundary layers are less stable than lower layers and tend to delaminate. In delaminating, these upper boundary layers form vortical flow patterns which dissipate energy but do not contribute significantly to the net movement of the fluid which is the motive force for propulsion in these devices. Furthermore, the thickening and delamination of the upper boundary layers can also cause thickening and delamination (breakdown) of the Prandtl layer which will disrupt fluid flow until the Prandtl layer is re-established and stabilizes. This type of boundary layer instability in part caused by the differential velocity between the centre of rotation of a fluid moving member and the velocity of the outer edges of a fluid moving member. The existence of the Prandtl layer is required for a fluid moving member to effectively transfer energy to the fluid. Therefore preventing degradation of the Prandtl layer (eg. the collapse of the Prandtl layer due to the sudden thickening of the Prandtl layer) increases the efficiency of the fluid moving member.
In accordance with the instant invention, power is delivered to the fluid moving member to prevent the Prandtl layer from collapsing or delaminating and to reduce vorticity caused by other boundary layers collapsing. By maintaining an effective Prandtl layer on the fluid moving member for a greater time, more of the energy which is input into the system to cause the fluid moving member to rotate will be transmitted to the fluid passing over the fluid moving member. Accordingly, a pulse train is modulated to vary the acceleration (which may be negative acceleration, i.e. a deceleration) of the fluid moving member to reduce the degradation of the Prandtl layer and other boundary layers which form when the fluid moving member moves through the fluid for systems directly driven by an electric motor. Alternately, the desired acceleration and deceleration of the fluid moving member can be achieved by applying a pulse train signal to an electromagnetic clutch which couples a prime mover to the fluid moving member. In the case of an electromagnetic clutch, the series of electrical pulses cause differential slip to occur in the clutch thereby accelerating and decelerating the fluid moving member. A further alternative method produces the desired acceleration and deceleration of the fluid moving member by applying a pulse train of hydraulic pressure pulses to a hydraulic mechanical clutch which couples a prime mover to the fluid moving member. In the case of an hydraulic mechanical clutch, the series of pressure pulses cause differential slip to occur in the clutch thereby accelerating and decelerating the fluid moving member. A fourth alternative method applies to a design wherein a gasoline or diesel engine is the prime mover which is directly coupled to the fluid moving member. In this fourth example, the fuel flow rate and/or the spark temperature are modulated such that a reduced amount of fuel or lesser spark would decelerate the output shaft while extra fuel and a higher spark temperature would accelerate the output shaft. In this manner the desired accelerations and decelerations could be created.
The cyclic thickening of the boundary layer on the fluid moving member occurs when the power is supplied uniformly to the fluid moving member. In accordance with the instant invention, the fluid moving member is decelerated (i.e. the rate of rotation reduced) prior to the Prandtl layer collapsing or delaminating. When the fluid moving member is decelerated, the Prandtl layer begins to thin and would otherwise collapse if the relative motion between the fluid and the fluid moving member is reduced to below a critical threshold velocity. Therefore, the fluid moving member is again accelerated to maintain the Prandtl layer and other boundary layers within a thickness range which is optimal for transmitting energy from the fluid moving member to the fluid.
Another aspect of the instant invention relates to the acoustic signature which is produced when the fluid moving member and its associated drive mechanism are accelerated and decelerated to prevent the Prandtl layer from collapsing or delaminating and to reduce vorticity caused by other boundary layers collapsing. By maintaining an effective Prandtl layer on the fluid moving member for a greater time, less energy is transferred to vorticity resulting in reduced noise generation. Hence a vessel would operate more silently. In addition, a specific acoustic signature could be created by controlling the pulse train so as to modulate the acceleration of the fluid moving member to produce the desired acoustic signature. Alternately, the desired acceleration and deceleration to produce the desired acoustic signature can be achieved by applying a pulse train signal to an electromagnetic clutch which couples a prime mover to the fluid moving member. In the case of an electromagnetic clutch, the series of electrical pulses cause differential slip to occur in the clutch thereby accelerating and decelerating the fluid moving member. A further alternative method produces the desired acceleration and deceleration of the fluid moving member by applying a pulse train of hydraulic pressure pulses to an hydraulic mechanical clutch which couples a prime mover to the fluid moving member. In the case of a hydraulic mechanical clutch, the series of pressure pulses cause differential slip to occur in the clutch thereby accelerating and decelerating the fluid moving member. A fourth alternative method applies to a design wherein a gasoline or diesel engine is the prime mover which is directly cooled to the fluid moving member. In this fourth example, the fuel flow rate and/or the spark temperature are modulated such that a reduced amount of fuel or lesser spark would decelerate the output shaft while extra fuel and a higher spark temperature would accelerate the output shaft. In this manner the desired accelerations and decelerations could be created to control the acoustic signature of the drive system.
This invention has particular applicability to aircraft, surface vessels, sub-surface vessels, missiles and torpedoes. As such, the prime mover is typically attached to the hull of the vessel or fuselage of the aircraft or missile so as to translate the thrust from the fluid moving member such as a propeller, impeller, or turbine assembly. What the inventor has realized is that if the drive system of the fluid moving member is configured so as to cause deceleration just prior to the collapse or delamination of the Prandtl layer, and to accelerate shortly thereafter to re-thicken or re-establish the Prandtl layer and prevent it from completely collapsing. Thus the Prandtl layer simply reduces or thins down rather than collapse or delaminate. Further, the acceleration results in the Prandtl layer being built up faster. In effect, this reduces the vortex energy thrown off from the blade, and hence significantly reduces energy losses. Accordingly, the algorithm for the pulse train for a vacuum cleaner should be developed, with this in mind. This is done simply by running a series of tests or experiments on the complete system or a scale model thereof, which will allow for any effects which will alter the power consumption of the prime mover and/or control the acoustic signature.
Therefore, in one aspect of the invention, there is provided a method of moving a fluid using a fluid moving member, the method comprises providing power to rotate the fluid moving member and form a Prandtl layer of fluid on the fluid moving member as the fluid moving member moves and, varying the rate of rotation of the fluid moving member to reduce the degradation of the Prandtl layer as the fluid travels over the fluid moving member. The fluid moving member may comprise the power transfer member of a pump and the method further comprises driving the fluid moving member to cause the fluid to flow.